1. Field of the Invention
The invention relates generally to devices and methods for improved gravel packing operations within a wellbore. In more particular aspects, the invention relates to the design of devices that are used to place gravel or other solids in such operations.
2. Description of the Related Art
During gravel packing, a slurry containing gravel or a proppant is pumped down a tubing string into a wellbore and placed where desired using a cross-over tool with suitable exit ports for placement of the gravel in desired locations within the wellbore. A typical conventional gravel packing cross-over tool is described, for example, in U.S. Pat. No. 6,702,020, issued to Zachman et al. This patent is owned by the assignee of the present invention and is hereby incorporated by reference.
Gravel packing operations create significant erosion wear upon the components of the cross-over assembly as the gravel or proppant is flowed into the wellbore. One area that tends to receive the most severe damage is around the exit aperture where the solid material exits the crossover tool through a slurry flow port and enters the inside of the production assembly. In order to counter wear damage a wear sleeve, or blast liner, is typically placed around the crossover tool proximate the slurry flow port. A number of gravel exit ports are then circumferentially spaced around the lower end of the wear sleeve or blast liner to distribute the solid material into the entire surrounding annulus. However, the addition of a blast liner provides only a limited amount of protection for the device.
A problem that has been recognized by the inventor is that gravel packing systems of this type are limited in their ability to handle ultra high rate proppant slurry flows. Solid material exiting the slurry flow port of the cross-over tool tends to gather in the space between the outer surface of the cross-over tool and the inner surface of the wear sleeve on only one side of that space. As a result, the solid material is not evenly distributed when exiting the wear sleeve.
An additional problem with conventional gravel packing systems is the erosion of the wear sleeve or blast liner. Flow capacity for existing slurry flow ports has been exceeded by recent demands that systems pump 40-60 barrels per minute of slurry and large total proppant volumes, often exceeding 1 million pounds. The velocity of the proppant slurry leaving the slurry flow port, coupled with the larger flow volumes, causes erosion and ultimate failure of the wear sleeve and production assembly adjacent the flow port.
The present invention addresses the problems of the prior art.